The broad long-term objectives of the proposed research include an increased understanding of both the organization of memory in the mammalian brain, and the neurochemical bases of different forms of memory. These objectives will be accomplished through experimental linkage of two sets of previous findings: l) the hippocampal system and caudate nucleus are parts of independent brain memory systems, and 2) the amygdala plays a general modulatory role in memory, mediating the memory-enhancing effects of drugs affecting many neurotransmitter systems. The specific aims of the proposed research include an examination of three primary hypotheses: 1) the modulatory role of the amygdala in memory extends to different forms of memory. 2) the modulatory influences of the amygdala on memory involve dissociable effects on hippocampal and caudate nucleus memory systems, and are mediated by amygdala output via the stria terminalis. 3) the neurochemical bases of memory processes mediated by the amygdala, hippocampus and caudate nucleus involve brain dopaminergic systems. The research design and methods combine central nervous system manipulations in rats, including brain lesions and post-training intracerebral microinjections of dopaminergic agonist drugs. Rats will receive training in either a hippocampal-dependent spatial water maze task, or a caudate nucleus-dependent cued water maze task. The two tasks require rats to swim to an escape platform within a circular maze. In the hippocampal-dependent spatial task, the hidden escape platform is in a constant location, and can be located only by learning spatial relationships among distal extramaze cues. In the caudate nucleus- dependent cued task, rats are trained to swim to a visible cue mounted on a platform which is placed in a different spatial location on each trial. Immediately post-training, animals will receive intracerebral (hippocampus, caudate nucleus, or amygdala)injection of a dopamine receptor agonist or vehicle. 24 hours later rats will receive a retention test in which latency to mount the platform will be used as a measure of the previous day's training. In other groups of rats, intracerebral injections of dopaminergic agonists will be combined with lesions of the stria terminalis, in order to assess the anatomical bases of amygdala modulation of multiple memory systems. The separable roles of the hippocampal system and caudate nucleus in memory which has been established in rodents is also observable in humans with neurological disorders compromising these two brain regions. Thus, increased knowledge of the anatomical and neurochemical bases of multiple memory systems may have important implications for understanding the biological bases of human learning and memory processes.